Khaled Sharrouf and boys believed to be his three sons (one not visible) stand in front of the Islamic State flag in an image posted on Twitter. Source: SuppliedSource:Twitter

LESS than three months after his Twitter photo of his seven-year-old son holding a decapitated head shot him to worldwide infamy, Khaled Sharrouf, a 33-year-old married father of five from the south west suburbs of Sydney remains in Syria.

It is believed he is fighting with an estimated 60 other Australians for Islamic State extremists, many of them recruited by former Kings Cross bouncer Mohammad Ali Baryalei who is thought to have been killed during the week.

The Twitter picture that disgusted the world ... Khaled Sharrouf’s son holds the decapitated head of a soldier in the Syrian city of Raqqa. Source: SuppliedSource:Twitter

But how Sharrouf, who was on a watch list after being convicted of a terrorist offence in 2005 — the biggest terrorism plot in Australian history — was able to leave Australia on his brother’s passport is one of the questions Four Corners aims to have answered on Monday night.

Reporter Marian Wilkinson spoke to a Muslim community leader who has one explanation for why he fled Australia under his brother’s name.

“I believe that Khaled Sharrouf was afraid for his life and that’s what made him decide to leave Australia and use his brother’s passport to escape, because he was concerned that he will be the next one to be shot.”

Four Corners found evidence Sharrouf, who’d become something of a thug for hire in the local building industry, had come to the attention of the law after an alleged extortion threat against one of Australia’s most prominent construction companies.

“He certainly appears to have become involved with some people who were involved in some pretty serious criminal activity and a couple of people in fact who were murdered, ultimately,” one police officer tells Four Corners.

Mental illness had ‘influenced his radicalisation’ ... Khaled Sharrouf and boys believed to be his three sons (one not visible) stand in front of the Islamic State flag in an image posted on Twitter. Source: SuppliedSource:Twitter

Sharrouf, who dropped out of school, emerges as a complex mix of mentally ill and canny self-promoter who pulled off Islamic State’s most spectacular PR stunt.

Four Corners looks at what part Sharrouf’s schizophrenia played in his drift into extremism.

“Khaled Sharrouf is not bad, he’s mad,” his former lawyer tells Wilkinson.

“There’s no less than five psychiatrists that I know who have diagnosed him with very significant mental health issues.”

“He was very ill mentally. He had very severe schizophrenia, he suffered from delusions — every report was very clear on this point,” Justice Whealy, who presided over the 2005 terrorism trials, told ABC’s 7.30.

In a report tendered to the Supreme Court, Sharrouf’s psychiatrist Stephen Allnutt said his patient’s mental illness had influenced his radicalisation, according to an earlier story on ABC News.